The leakage current protection device, or the ground fault circuit interrupter, is used to detect the ground fault current in electrical systems, instruments, devices, equipment and power supply systems, when the ground fault current exceeds a specified limit, the circuit protection device will automatically shut down the power supply and so as to protect human being and properties. In actual application, the leakage current protection device or the ground fault circuit interrupter may partly or wholly malfunction, and their protection functions thereby malfunction, and safety risk may occur without the knowledge of the users.
To solve the problems above, some leakage current protection devices are designed according to standard such as IEC 61008-1, IEC 61009-1, GB 6829.1 and have a test button, but their users have to depress the test button periodically to test whether the circuit protection function is working properly. For one aspect, it increases users' workload, and for another, during the periodic test, the power supply must be cut off, and that causes inconvenience to users. Thirdly, if the users do not periodically test the circuit, or the circuit protection device malfunctions between two periodic tests (such as one month), the users may not timely discover that the circuit protection device loses protection ability and safety risk may similarly occur.
To solve the problems mentioned above, some ground fault circuit interrupters designed according to UL 943 standard are available with self fault detection functions to detect and diagnose the operation condition of the ground fault circuit interrupter, and generate alarming signals when the ground fault circuit interruption function fails. Some ground fault circuit interrupters are provided with self fault detecting, alarming and protection interruption functions, but their structure are complex, so it results in manufacturing difficulties and high cost, and thus the reliability of the circuit protection function of the device is reduced, and safety risk may occur.